What isn't cool is that WotC allows this in a way that poisons the content you create. If you write the Rapan Athuk adventure for 4e - great! but now you can't publish Rapan Athuk 3e, or True20, adventures - not so great, but acceptable. What's really got people in a tangle is that when 4e ends, and the GSL is hence revoked - you can't take Rapan Athuk and publish it under the OGL, under the Pathfinder Tenth Edition rules. You arguably can't even publish it under any other system, or into the public domain, as WotC is the sole judge of what's part of the same "product line", and may look at the content in deciding that. That's just has nothing to do with being allowed to make supplements rather than variant games, it goes way beyond that.